Medial treatments for diseases, such as origin of arrhythmia and arteriosclerosis, have been proposed in, for example, Jpn. Pat. Nos. 2538375, 2510428 and 2574119, U.S. Pat. No. 6,491,710 B2 and JP 2003-120850 A (JP '850). Those known medical treatments use an inflatable balloon internally provided with a radio-frequency electrode. A radio-frequency electric field is created around the radio-frequency electrode to heat tissues in contact with the balloon for treatment.
Tissues in contact with a balloon need to be heated as uniformly as possible to treat the tissues satisfactorily. A radio-frequency electrode having a three-dimensional shape cannot be disposed in perfect alignment with the balloon inside the balloon and hence the liquid contained in the balloon is heated irregularly. In addition, the liquid inside the balloon is heated unavoidably in a non-uniform temperature distribution due to convention. Hence tissues in contact with the balloon cannot be uniformly heated.